Therapeutic dynamic seating devices that deliver musculoskeletal training to the sitter have been disclosed in various forms in the prior art. Oftentimes it is desirable to have a non-static orientation of a seating plane to provide the human body with a platform that will reposition a certain amount. Oftentimes, as described herein below, a properly designed dynamic seating system providing a non-static support has the unexpected advantage of allowing a body to readjust in a more bio-mechanically naturally aligned orientation. For a non-static seating arrangement to deliver the maximum therapeutic benefits to the sitter it will have to entice the sitter to actively participate in the sitting process. Active participation means that the seating system encourages the sitter's neuromuscular system to assume a dynamic posture by itself. Forcing active participation through periodic external movement of the seat as is done in passive dynamic seating will cause the body to fight the seat movement as an intrusion and defeat the benefits gained by the dynamic environment. For an active system to work properly it will have to detect the movement of the sitter and apply a modulation with the proper phase relationship between the sitter's movement and the seat modulation to the seat. This mechanism is known as a phaselocked loop servo system. Also the amplitude of the external modulation must be small enough that the sitter's neuromuscular system does not consider the movement as intrusive.
Other devices, such as regular seating members, provide a substantially horizontal surface, or a surface that is at least horizontal in the lateral direction with respect to the hips of the individual sitting thereon. This sitting arrangement provides a static sitting environment for the user. Neurological research has shown that proper posture can only be achieved if the sitter is allowed to move in both the lateral and transverse direction to properly activate the proprioceptive system of the sitter in a way similar to the movement experienced during horseback riding, which activates both the vestibular as well as the kinesthetic muscle sensors. Continuous movement triggering the deep layer muscles along the spine that are connecting individual vertebrae to “fire” afferent nerve signals to the cerebellum is responsible in conjunction with inputs from the vestibular and vision sensors, for the maintaining of a healthy posture. The internal stabilizers, i.e., the deep layer muscles along the spine must be strengthened before any healing of a back injury can take place. If the deep layer muscles are not firing properly further injury to the back will result. The exercises to the deep layer muscles are very specific and must lead to a symmetric activation without the activation of the large outer layer muscles.
Static sitting postures will lead to lower back pain (as anybody who has sat confined to an airplane seat for a long distance flight can attest to) and eventually back injuries like bulged discs and sciatica as well as pressure ulcers when the individual is bound to the sitting surface as is the case in wheelchairs. This negative consequence of a static seating device is more detrimental to the sitter when the sitter is afflicted with a neuro-muscular impairment like cerebral palsy. Devices such as gym balls (also referred to as Swiss balls), which generally are rather large balls of approximately 2 feet (or more) in diameter and filled with air, are utilized sometimes to provide a non-static/non-stable environment to sit upon. However, in general, while sitting upon these devices, the contact point functions as a possible initial point of rotation, and the sitting point is generally at the apex to this contact point in the upper region. Sitting on such a device feels like sitting on a stick with the pivoting point at the ground. This type of configuration does not mimic the dynamics of therapeutic horseback riding and is therefore limited in its ability to deliver the desired therapeutic benefits that are associated with hippo/equestrian therapy. Hippotherapy delivers continuous triggering of the deep layer muscles along the spine, proprioceptors, and also triggers the vestibular system for proper stabilizing action by the cerebellum as well as the sensorimotor cortex in the human brain.
In order for the information from the proprioceptors and the vestibular system to reach the sensorimotor cortex it must pass the gate keeper for the cortex, the hippocampus, and be judged as safe. If the information does not feel safe, the hippocampus activates the lower brain and sets up the fight or flight mode, in which only a limited amount of information gets registered by the cortex. The fight or flight mode gets triggered when, in the case of a dynamic seating system, the sitter has the feeling of falling over or losing balance.
Anyone who has sat on such device, meaning a ball-based chair or stool design or a device with an improperly designed dynamic coupling between the seat and the post of a chair, can attest that these devices feel unsafe to the user and leave the user focusing on the task of not falling over. Unfortunately, when shifting left or right, the further one travels from this center orientation, the further the user is dropping and hence there is a greater amount of rotational force exerted on the individual to continue rotating in this off-centered direction. In other words, the greater distance from the contact point of the ball to the ground to the actual sitting engagement region can cause a sideward rolling action. This sideward rolling will cause the entire upper body to shift sideward adding the need for the sitter to move the entire upper body back to centerline instead of having the body tilt just around the midline of the spine as is desirable and achieved when the pivot point is in direct contact with the pelvis, as is done when sitting on a horse, and provide the necessary input for the proper functioning of the proprioceptive system.
Using a ball as therapeutic device for individuals suffering from cerebral palsy (a sensory input dysfunction caused by brain injury) induced scoliosis will cause the sitter to use more of his/her non-affected neuromuscular system to compensate for the inactivity of the impaired part to stay balanced, i.e., he/she will lean even more into his/her curve, create an even tighter muscle tone because of fear to fall over. This approach will aggravate an already fragile situation even further.
In contrast, a properly designed dynamic seating system as described herein will place the sitter's pelvis into direct contact with the axis of rotation and use a joint technology that will make the sitter feel safe and wanting to move instead of being afraid of losing balance. Under such conditions the sitter will stay relaxed and “wiggle” his/her pelvis creating the desirable afferent nerve signals arising from the deep layer muscles along the spine that are required for a healthy posture.
With regard to a properly designed dynamic seating system, as described herein the sitter can assume a posture that allows him/her to most effectively compensate for the forces of gravity without the excessive use of the large outer layer muscles. In the case of scoliosis the seat will rotate slightly into the direction of the sitter's primary curve allowing for a more relaxed secondary and tertiary (where applicable) compensatory curve resulting in a much more erect sitting posture. This more erect sitting posture leads to a reduction in the wedging of the spinal discs and therefore less pinching of the nerves in the compressed region. Further, present analysis indicates that the overall curve of a spine with an individual having scoliosis is reduced, because the sitter can find his/her center of gravity more easily and therefore does not have to overcompensate as strongly as when sitting on a flat surface. Present analysis has also found that utilizing the device as described herein has the effect of improving posture and sense of balance for the seated individual, able-bodied or disabled alike, because it successfully triggers both the proprioceptors along the spine and the sensors of the vestibular system in a safe manner, such that the sensorimotor cortex receives meaningful information which it can process.
In addition to side-to-side tilting the seat also has to tilt in the anterior/posterior direction, to allow the angle between chest and femur to open up and to reduce the extension of the hamstrings. A relative angle of 90° and smaller will stretch the hamstrings too much and lead to a backward pull on the spine, causing it to go into a C-shape and causing pinching at the front end of the discs. Providing a system where the hips are allowed to tilt forward about a lateral axis provides a more desirable pressure distribution upon the lumbar vertebrae. As described herein, the system is designed to adapt to a users' physiology, allow the user to sit with a more upright posture and to “wiggle” his/her pelvis for better proprioception. Placing the axis of rotation closer to the pelvis enables the user to tilt his/her pelvis in a manner that does not require a conscious effort on behalf of the sitter and the use of the large outer layer muscles to stay balanced and therefore to obtain a posture that is well balanced within the individual's physiological framework, and therefore enables the user who is afflicted with, say, scoliosis to obtain a better balanced posture with an overall reduced curvature of the spine.
Using the same device mechanism in the embodiment of an exercise device called balance board can be used for rehabilitation injuries of the lower extremities, like foot, ankle, knee or hip injuries and the regaining of a sense of balance periods of immobility.